This seems totally crazy... as part of trying to work out what the intermittent starting problem with my 16V is, I tried running it with the ECU relay unplugged to see if that reproduced the symptoms.
I was fairly sure it would crank without starting... but it starts and runs! Can anyone explain that?!
I'm confident it was the ECU relay I removed, it was in the position marked in the manual, and labelled 30.